Hot water appliance

ABSTRACT

A hot water appliance  10  comprises a water tank  12  provided with a water tank wall  14 . The hot water appliance  10  further comprises a vacuum vessel  20  which encloses a vacuum space V. The water tank  12  is wholly included in the vacuum space, and the whole water tank wall  14  is bounded by vacuum. The vacuum vessel  20  is provided with a vacuum vessel wall  22  which consists of a number of vacuum vessel wall parts that are gastightly connected with each other by welding or soldering. Further, the hot water appliance  10  comprises at least one functional pipe  100, 200, 300, 400, 500  which extends through the water tank wall  14  and is gastightly connected with the water tank wall  14  at the location of a water tank wall connection  18 . The functional pipe  100, 200, 300, 400, 500  also extends through the vacuum vessel wall  22  and is gastightly connected with the vacuum vessel wall  22  at the location of a vacuum vessel wall connection  24.

FIELD

The invention relates to a hot water appliance for heating and holding hot water at a desired temperature, and which is connectable to a public water supply and to a kitchen tap.

BACKGROUND

EP 1 173 715 describes a hot water appliance comprising a hot water tank and a vacuum insulation. The construction of the hot water appliance described therein is especially suitable for storing pressurized water of a temperature of more than 100° C., so that upon dispensing of the stored water, for instance via a draw-off tap, instantaneously boiling water is dispensed. In the hot water tank is an electric heating element which heats the water and holds it at a desired temperature. Also provided is a temperature sensor, as well as a water supply pipe which is connectable to the public water supply system and a water discharge pipe which is for instance connectable to a draw-off tap. In EP 1 173 715 the upper side of the water tank is provided with a flange on which a detachable cover is mounted with bolts. On top of the detachable cover, the hot water appliance is provided with an insulation material to minimize heat loss via the cover. In order to further limit the heat loss at the top between the hot tank and the cool outer jacket, the connection between reservoir and jacket is implemented as a thin-walled ring-shaped collar with which the tank is suspendedly connected to the jacket. Due to the thermal resistance of this collar, the direct heat conduction loss between the hot tank and the cool jacket is limited.

SUMMARY

The invention contemplates the provision of a hot water appliance that has a still better efficiency than the hot water appliance known from the prior art. That is to say, a hot water appliance with which even less heat is lost in keeping the hot water in the water tank of the hot water appliance at the storage temperature.

To this end, the invention provides a hot water appliance according to claim 1. More particularly, the invention provides a hot water appliance comprising:

-   -   a water tank comprising a water tank wall;     -   a heating element included in the water tank;     -   a vacuum vessel enclosing a vacuum space, the water tank being         wholly included in the vacuum space, the whole water tank wall         being bounded by vacuum, the vacuum vessel comprising a vacuum         vessel wall consisting of a number of vacuum vessel wall parts         gastightly connected with each other by welding or soldering;         and     -   at least one functional pipe extending through the water tank         wall and being gastightly connected with the water tank wall at         the location of a water tank wall connection, and the functional         pipe also extending through the vacuum vessel wall and being         gastightly connected with the vacuum vessel wall at the location         of a vacuum vessel wall connection.

In the hot water appliance according to the invention, the water tank is wholly enclosed by a vacuum jacket. This is in contrast to the hot water appliance described in the background section, where on the cover of the water tank, insulation material was placed and no vacuum jacket was present. With the configuration according to the invention, a still better insulation is obtained, as a result of which less heat loss occurs. Also, the heat conduction loss of the collar-shaped connection between tank and vacuum jacket of the hot water appliance as described in the background section is absent because the tank is wholly enclosed by a vacuum space.

Further, the hot water appliance according to the invention has a more compact and a simplified and lighter construction due to the redundancy of the cover, the collar-shaped connection between tank and vacuum jacket, and the associated required insulation material above the cover of the hot water appliance as described in the background section.

In addition, by virtue of its simplified construction, the hot water appliance according to the invention consists almost entirely of metal parts, in consequence of which it is properly and sustainably recyclable and can be produced at lower cost.

The hot water appliance according to the invention is of particular advantage when so-called boiling water appliances are used. The volume then typically amounts to 20 liters at a maximum, more particularly the volume is preferably in the range of 3 to 8 liters. The holding temperature of the water in the tank is 90° C. at a minimum and is preferably in the range of 105° C.-108° C. The pressure in the vacuum space is preferably 10⁻⁴ mbar, preferably at least 10⁻⁵ mbar.

Given a water tank volume of for instance 3 liters and a holding temperature of 108° C., the hot water appliance according to the invention enables a heat loss of the hot water tank of approximately 2 W to be realized, 0.5 W of which is conduction loss and 1.5 W radiation loss.

In an embodiment, the water tank may be exclusively borne by the at least one functional pipe.

By a functional pipe is meant a pipe that must in any case be present for fulfilling a different function than bearing the water tank. A functional pipe can be, for example, a water supply pipe or a water discharge pipe. Also, it may be a pipe for therein including particular components such as electric cabling, an electric heating element and/or a temperature sensor. Such pipes have to extend into the interior of the water tank and so must also pass the vacuum vessel wall. In consequence of this, these pipes form a path of heat conduction from the water tank to the vacuum vessel wall. However, the presence of a number of these functional pipes is necessary and by presently providing these with yet another, second function, namely, bearing or supporting the water tank in the vacuum vessel, there is not, for this second function, an extra heat conduction bridge between the water tank wall and the vacuum vessel wall being created.

In an embodiment, the weight of the water tank may be transferred via the at least one functional pipe to the vacuum vessel wall. In this embodiment, further, the vacuum vessel wall, in turn, can serve for support of the whole hot water appliance on a flat plane/surface. In an alternative embodiment, it would also be possible to connect the functional pipes with a fixed object of the external world, so that the weight of the hot water appliance is transferred directly via the at least one functional pipe to the fixed object of the external world.

A part of the at least one functional pipe that extends between the water tank wall connection and the vacuum vessel wall connection determines a heat transport length l_(h) for heat conduction from the water tank wall connection to the vacuum vessel wall connection and has a wall sectional area A. When ribbed or bellows-shaped functional pipes are used, the heat transport length l_(h) may be greater than the pipe length. In an embodiment, a ratio between heat transport length l_(h) in mm and wall sectional area A in mm² can satisfy the formula l_(h)/A>4 mm⁻¹. Given a heat transport length/wall sectional area quotient in that range, the heat conduction via the at least one functional pipe can be limited such that the heat losses via the at least one functional pipe through heat conduction are virtually negligible.

A similar slight heat loss may also be effected with an embodiment where the part of the at least one functional pipe that extends between the water tank wall connection and the vacuum vessel wall connection has a heat transport length l_(h) that is greater than 60 mm. In addition, the material of the at least one functional pipe is preferably stainless steel or a like metal having a relatively low heat conductivity coefficient. Certainly when also the wall thickness of the stainless steel functional pipes is then in the range of 0.4 to 1.0 mm and the diameter is less than 8 mm, heat conduction from the water tank to the vacuum vessel wall via the at least one functional pipe may be negligible.

The water tank can comprise a cylindrical water tank sidewall and the vacuum vessel can comprise a cylindrical vacuum vessel sidewall. To augment the efficiency of the hot water appliance still further, in an embodiment, at least between the cylindrical water tank sidewall and the cylindrical vacuum vessel sidewall, a laminate of reflecting foil and glass fiber cloth may be included.

Further elaborations of the invention are described in the dependent claims and will hereinafter be further clarified with reference to one or more examples in the drawings.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 shows schematically a cross-sectional view of a first embodiment of the hot water appliance;

FIG. 2 shows schematically a cross-sectional view of a second embodiment of the hot water appliance;

FIG. 3 shows schematically a cross-sectional view of a third embodiment of the hot water appliance;

FIG. 4 shows an example of the embodiment represented schematically in FIG. 3 ; and

FIG. 5 shows a perspective cross-sectional view of the example from FIG. 4 .

DETAILED DESCRIPTION

In the following detailed description, corresponding parts of the different embodiments are designated with the same reference numerals. The detailed description does not relate exclusively to the examples represented in the figures. The reference numerals specified in the detailed description and the claims have no limiting effect and are only for clarification by referring to examples represented in the figures, of the various embodiments that are discussed in the detailed description.

In the most general terms, the invention relates to a hot water appliance 10 which comprises a water tank 12 provided with a water tank wall 14. Included in the water tank 12 is a heating element 28. The hot water appliance 10 further comprises a vacuum vessel 20 which encloses a vacuum space V. The water tank 12 is wholly included in the vacuum space and the whole water tank wall 14 is bounded by vacuum. The vacuum vessel 20 is provided with a vacuum vessel wall 22 which consists of a number of vacuum vessel parts which are gastightly connected with each other by welding or soldering. Further, the hot water appliance 10 comprises at least one functional pipe 100, 200, 300, 400, 500 which extends through the water tank wall 14 and is gastightly connected with the water tank wall 14 at the location of a water tank wall connection 18. The functional pipe 100, 200, 300, 400, 500 extends also through the vacuum vessel wall 22 and is gastightly connected with the vacuum vessel wall 22 at the location of a vacuum vessel wall connection 24.

The advantages of the hot water appliance as indicated above in its most general terms have already been described in the summary and the advantages described there are understood to be inserted here by reference.

In the embodiment of which an example is schematically represented in FIG. 1 , the water tank 12 may be supported by a number of supports 16. Preferably, these supports 16 are implemented in a material that conducts heat poorly and also releases as few gases as possible, so that the vacuum in the vacuum space V is not disturbed. Further, it is preferred that the contact area between the supports 16 and the water tank 12 is as small as possible to limit the heat conduction via the supports 16 to a minimum.

As has already been described above in the summary, in an embodiment, of which examples are shown in FIGS. 2-4 , the water tank 12 may be borne exclusively by the at least one functional pipe 100, 200, 300, 400 and/or 500. In addition, in a further elaboration of this embodiment, the weight of the water tank 12 may be transferred via the at least one functional pipe 100, 200, 300, 400 and/or 500 to the vacuum vessel wall 22.

A part of the at least one functional pipe 100, 200, 300, 400 and/or 500 that extends between the water tank wall connection 18 and the vacuum wall connection 24 has a heat transport length l_(h) and a wall sectional area A. In an embodiment, a ratio between the heat transport length l_(h) in mm and the wall sectional area A in mm² can satisfy the formula l_(h)/A>4 mm⁻¹.

In an embodiment, the part of the at least one functional pipe 100, 200, 300, 400 and/or 500 that extends between the water tank wall connection 18 and the vacuum vessel wall connection 24 can have a heat transport length l_(h) that is greater than 60 mm. In addition, the material of the at least one functional pipe is preferably one of stainless steel, titanium or Incoloy, respectively.

In an exemplary embodiment, of which an example is shown in FIGS. 1-5 , the at least one functional pipe 100, 200, 300, 400 and/or 500 can have an external diameter that is less than 8 mm.

In addition, it is preferred that the at least one functional pipe 100, 200, 300, 400 and/or 500 has a wall thickness that is between 0.4 and 1.0 mm.

In an embodiment, the earlier-mentioned water tank wall connection 18 between the at least one functional pipe and the water tank wall, and the vacuum vessel wall connection 24 between the at least one functional pipe and the vacuum vessel wall, can be welded joints.

In an alternative embodiment, the water tank wall connection 18 between the at least one functional pipe and the water tank wall, and the vacuum vessel wall connection 24 between the at least one functional pipe and the vacuum vessel wall, can be soldered joints.

In an embodiment, of which examples are shown in FIGS. 1-5 , the at least one functional pipe 100, 200, 300, 400 and/or 500 can comprise at least one of a water supply pipe 100, a water discharge pipe 200, an electric heating element containing pipe 300, 400, and a temperature sensor containing pipe 500.

In an embodiment, of which an example is shown in FIGS. 1-5 , the water tank 12 can comprise a cylindrical water tank sidewall, and the vacuum vessel 20 can contain a cylindrical vacuum vessel sidewall. In addition, at least between the cylindrical water tank sidewall and the cylindrical vacuum vessel sidewall, for reduction of the radiation loss, a laminate of reflecting foil and glass fiber cloth may be included.

A good reduction of radiation loss is for instance obtained when the laminate comprises at least three layers of reflecting foil and at least three layers of glass fiber cloth.

In an embodiment, of which an example is shown in FIGS. 3, 4 and 5 , the at least one functional pipe 100, 200, 300, 400, 500 may be provided with a first pipe part 102, 202, 302, 402, 502, a first bend 104, 204, 304, 404, 504 which connects the first pipe part 102, 202, 302, 402, 502 with a second pipe part 106, 206, 306, 406, 506, a second bend 108, 208, 308, 408, 508 which connects the second pipe part 106, 206, 306, 406, 506 with a third pipe part 110, 210, 310, 410, 510. The first pipe part 102, 202, 302, 402, 502 then extends through an upper side of the vacuum vessel 20. The third pipe part 110, 210, 310, 410, 510 extends through an underside of the water tank 12. Further, the first pipe part 102, 202, 302, 402, 502 extends substantially vertically between the water tank wall 14 and the vacuum vessel wall 22.

Such an embodiment has the advantage that the first pipe parts are particularly long, so that the heat transfer via those first pipe parts to the vacuum vessel wall 22 is limited to a far-reaching extent.

In an embodiment, of which an example is shown in FIGS. 3, 4 and 5 , the at least one functional pipe comprises:

-   -   a first functional pipe 100 which is a water supply pipe that         extends through and is gastightly connected with a first vacuum         top wall opening and which extends through and is gastightly         connected with a first water tank bottom wall opening;     -   a second functional pipe 200 which is a water discharge pipe         which extends through and is gastightly connected with a second         vacuum top wall opening and which extends through and is         gastightly connected with a second water tank bottom wall         opening;     -   a third functional pipe 300 which is a first heating element         pipe part which extends through and is gastightly connected with         a third vacuum top wall opening and which extends through and is         gastightly connected with a third water tank bottom wall         opening; and     -   a fourth functional pipe 400 which is a second heating element         pipe part which extends through and is gastightly connected with         a fourth vacuum top wall opening and which extends through and         is gastightly connected with a fourth water tank bottom wall         opening, wherein the third pipe 300 and the fourth pipe 400 are         mutually connected via a spiral pipe part 28, wherein the third         pipe 300, the fourth pipe 400 and the spiral pipe part 28 form         an integral one-piece part in which a heating element and         cabling to that heating element are included.

Finally, the at least one functional pipe may further comprise a fifth functional pipe 500 which is a sensor pipe which extends through and is gastightly connected with a fifth vacuum top wall opening and which extends through and is gastightly connected with a fifth water tank bottom wall opening. In the sensor pipe, at least a temperature sensor and cabling to that temperature sensor may be included.

In an embodiment, the water tank and the vacuum vessel can each have a cylindrical configuration. In addition, the first, second, third, the fourth and the fifth vacuum vessel top wall openings can each have a center which is located on a common pitch circle whose diameter is greater than an outer diameter of the cylindrical water tank and less than the inner diameter of the cylindrical vacuum vessel and whose center is located on a vertical axis of the cylindrical vacuum vessel.

The first, the second, the third, the fourth and the fifth, if any, water tank bottom wall openings each have a center which, according to an embodiment, may be located in a common vertical plane.

In an embodiment of which an example is shown in FIG. 5 , between the first pipe part 102, 202, 302, 402, 502 of the at least one functional pipe 100, 200, 300, 400, 500 and the vacuum vessel wall 22, a spacer 30 may be included which is manufactured from a material having a heat conductivity coefficient that is less than 5 W/(m·K), such as, for example, a ceramic ring. The spacer 30 may preferably be placed adjacent the transition between a water tank bottom side and a water tank sidewall.

In an embodiment of which an example is shown in FIGS. 4 and 5 the at least one first pipe part 102, 202, 302, 402, 502 may exclusively abut against the water tank wall 12 at a transition between a water tank bottom side and a water tank sidewall.

In an embodiment, of which an example is shown in FIGS. 4 and 5 , a transition of a water tank upper side and the water tank sidewall and an upper part of the at least first pipe part 102, 202, 302, 402, 502 can be located at a distance from each other.

In an embodiment, of which an example is shown in FIGS. 4 and 5 , the upper part of the at least first pipe part 102, 202, 302, 402, 502 and the water tank upper side may be fixed with respect to each other with the aid of a fixing element.

The fixing element can be a second spacer 32 of which an example is shown in FIGS. 4 and 5 . Such a second spacer 32 can keep the water tank 12 adjacent a transition of a water tank upper side and the water tank sidewall on the one hand, and an upper part of the first pipe part 102, 202, 302, 402, 502 of the at least one functional pipe 100, 200, 300, 400, 500 on the other, at a distance from each other. The second spacer 32 then engages, on the one hand, the water tank and, on the other, the upper part of the first pipe part 102, 202, 302, 402, 502 of the at least one functional pipe 100, 200, 300, 400, 500.

In further elaboration of this embodiment, the second spacer's 32 engagement of the water tank may be realized on the top of the water tank 12 at the location of the axis of the water tank 12. The second spacer's 32 engagement of the upper part of the first pipe part 102, 202, 302, 402, 502 of the at least one functional pipe 100, 200, 300, 400, 500 may be realized on one upper part or on two upper parts 102, 402.

The second spacer 32 is implemented in the example shown as a thin-walled element having a small sectional area so as to keep the heat conduction by the second spacer 32 from the water tank 12 to the first pipe parts 102, 402 as small as possible. The second spacer 32 can absorb both pressure forces and tensile forces, which is relevant for stabilization of the water tank 12 in the vacuum vessel 20, especially during transport of the hot water appliance, to prevent damaging.

The invention is not limited to the embodiments described nor to the examples shown in the figures. The figures and the reference numerals are for clarification only and have no limiting effect. The invention is defined by the appended claims. 

1. A hot water appliance comprising: a water tank comprising a water tank wall; a heating element included in the water tank; a vacuum vessel enclosing a vacuum space, the water tank being wholly included in the vacuum space, the whole water tank wall being bounded by vacuum, the vacuum vessel comprising a vacuum vessel wall consisting of a number of vacuum vessel wall parts gastightly connected with each other by welding or soldering; at least one functional pipe extending through the water tank wall and being gastightly connected with the water tank wall at the location of a water tank wall connection, and the functional pipe extending also through the vacuum vessel wall and being gastightly connected with the vacuum vessel wall at the location of a vacuum vessel wall connection.
 2. The hot water appliance according to claim 1, wherein the water tank is exclusively borne by the at least one functional pipe.
 3. The hot water appliance according to claim 2, wherein the weight of the water tank is transferred via the at least one functional pipe to the vacuum vessel wall.
 4. The hot water appliance according to claim 1, wherein a part of the at least one functional pipe that extends between the water tank wall connection and the vacuum vessel wall connection determines a heat transport length l_(h) for heat conduction from the water tank wall connection to the vacuum vessel wall connection and has a wall sectional area A, where a ratio between heat transport length l_(h) in mm and wall sectional area A in mm² satisfies the formula l_(h)/A>4 mm⁻¹.
 5. The hot water appliance according to claim 1, wherein the part of the at least one functional pipe that extends between the water tank wall connection and the vacuum vessel wall connection has a heat transport length l_(h) that is greater than 60 mm, wherein the material of the at least one functional pipe is one of stainless steel, titanium or Incoloy, respectively.
 6. The hot water appliance according to claim 1, wherein the at least one functional pipe has an external diameter that is less than 8 mm.
 7. The hot water appliance according to claim 1, wherein the at least one functional pipe has a wall thickness that is between 0.4 and 1.0 mm.
 8. The hot water appliance according to claim 1, wherein water tank wall connection and the vacuum vessel wall connection are welded joints.
 9. The hot water appliance according to claim 1, wherein water tank wall connection and the vacuum vessel wall connection are soldered joints.
 10. The hot water appliance according to claim 1, wherein the at least one functional pipe comprises at least one of a water supply pipe, a water discharge pipe, an electric heating element containing pipe, and a temperature sensor containing pipe.
 11. The hot water appliance according to claim 1, wherein the water tank comprises a cylindrical water tank sidewall and wherein the vacuum vessel comprises a cylindrical vacuum vessel sidewall, wherein at least between the cylindrical water tank sidewall and the cylindrical vacuum vessel sidewall, a laminate of reflecting foil and glass fiber cloth is included.
 12. The hot water appliance according to claim 11, wherein the laminate comprises at least three layers of reflecting foil and at least three layers of glass fiber cloth.
 13. The hot water appliance according to claim 1, wherein the at least one functional pipe comprises a first pipe part, a first bend which connects the first pipe part with a second pipe part, a second bend which connects the second pipe part with a third pipe part; wherein the first pipe part extends through an upper side of the vacuum vessel; wherein the third pipe part extends through a bottom side of the water tank; wherein the first pipe part extends substantially vertically between the water tank wall and the vacuum vessel wall.
 14. The hot water appliance according to claim 13, wherein the at least one functional pipe comprises: a first functional pipe which is a water supply pipe that extends through and is gastightly connected with a first vacuum top wall opening and which extends through and is gastightly connected with a first water tank bottom wall opening; a second functional pipe which is a water discharge pipe which extends through and is gastightly connected with a second vacuum top wall opening and which extends through and is gastightly connected with a second water tank bottom wall opening; a third functional pipe which is a first heating element pipe part which extends through and is gastightly connected with a third vacuum top wall opening and which extends through and is gastightly connected with a third water tank bottom wall opening; a fourth functional pipe which is a second heating element pipe part which extends through and is gastightly connected with a fourth vacuum top wall opening and which extends through and is gastightly connected with a fourth water tank bottom wall opening, wherein the third functional pipe and the fourth functional pipe are mutually connected via a spiral pipe part, wherein the third functional pipe, the fourth functional pipe and the spiral pipe part form an integral one-piece part in which a heating element and cabling to that heating element are included; and a fifth functional pipe which is a sensor pipe which extends through and is gastightly connected with a fifth vacuum top wall opening and which extends through and is gastightly connected with a fifth water tank bottom wall opening, wherein in the sensor pipe at least a temperature sensor and cabling to that temperature sensor are included.
 15. The hot water appliance according to claim 14, wherein the water tank and the vacuum vessel each have a cylindrical configuration, wherein the first, second, third, fourth and fifth vacuum vessel top wall openings each have a center which is located on a common pitch circle whose diameter is greater than an outer diameter of the cylindrical water tank and less than the inner diameter of the cylindrical vacuum vessel and whose center is located on a vertical axis of the cylindrical vacuum vessel.
 16. The hot water appliance according to claim 14, wherein the first, the second, the third, the fourth and the fifth water tank bottom wall openings each have a center located in a common vertical plane.
 17. The hot water appliance according to claim 13, wherein between the first pipe part of the at least one functional pipe and the vacuum vessel wall a first spacer is included which is manufactured from a material having a heat conductivity coefficient that is less than 5 W/(m·K).
 18. The hot water appliance according to claim 13, wherein the at least first pipe part exclusively abuts against the water tank wall at a transition between a water tank bottom side and a water tank sidewall.
 19. The hot water appliance according to claim 17, wherein a transition of a water tank upper side and the water tank sidewall and an upper part of the at least first pipe part are located at a distance from each other.
 20. The hot water appliance according to claim 19, wherein the upper part of the at least first pipe part and the water tank upper side are fixed with respect to each other with the aid of a fixing element.
 21. The hot water appliance according to claim 20, wherein the fixing element is implemented as a second spacer which keeps the water tank adjacent a transition of a water tank upper side and the water tank sidewall on the one hand, and an upper part of the first pipe part of the at least one functional pipe on the other, at a distance from each other, and which engages, on the one hand, the water tank and, on the other, the upper part of the first pipe part of the at least one functional pipe.
 22. The hot water appliance according to claim 21, wherein the second spacer's engagement of the water tank is realized on the upper side of the water tank at the location of the axis of the water tank and wherein the spacer's engagement of the upper part of the first pipe part of the at least one functional pipe is realized on one upper part or on two upper parts. 